Improvements in oil recovery are necessary to satisfy the present and future energy requirements of the United States and other countries of the world. As primary production of oil wells becomes exhausted, secondary or enhanced recovery becomes necessary to continue oil production. Steam injection is one of the most popular means of enhanced recovery of the present time.
The conventional method of use of steam is to generate it at the surface or above the ground and pump it down to the oil formation or subterranean petroliferous reservoir. However, because the steam rapidly loses heat and quality as it travels down the wellbore, this method is very wasteful of energy, particularly in that the greater the depth, the greater the loss of heat from the steam prior to reaching the petroliferous reservoir. Efficiencies up to 97% can be obtained by injecting the hot exhaust gases and steam into the oil reservoir with the down hole steam generator as compared to conventional surface steam generator efficiencies of 40-50%. This shows energy savings due to the fact that less fuel is required per unit of heat injected into the reservoir. Also, much of the heat generated in the conventional surface steam generator is lost to the atmosphere along with pollutants, out of the stack. Down hole steam generators may consume only 60% of the fuel volume for the same heating effect in the reservoir as compared to surface steam generators. Also there is a loss of efficiency in terms of oil recovery per unit of steam generated. Thus, a new method and a new steam generator for carrying out the method have been invented for generating the steam down hole near the oil formation. Accordingly, with this method and steam generator, depth of the well hole now makes little difference, if any, on the efficiency of the enhanced recovery.
For practical purposes, steam having a quality of 80% and thus having both a liquid phase and a vapor phase is preferred for being injected into a well. However, when these two phases of steam are injected down into a well in a subterranean petroliferous reservoir directly from the exit of the burner for enhanced oil recovery, which is now conventional, the heavier liquid phase has a tendency and inertia to continue straight down the well until it hits the bottom before being reflected towards the sides of the well where it then contacts the oil bearing or petroliferous formation, while the vapor phase tends to contact the sides of the well immediately and passes down the sides until it contacts the up coming liquid phase. The resultant effect is that the liquid phase mostly enters the bottom of the formation and the vapor phase mostly enters the upper portion of the formation with a resultant inefficient placement of non-uniform heat content fluids across the formation face. The new disclosed down hole steam generator subjects the complete well wall to both phases of the steam simultaneously for increased efficiency and oil production.